The present invention relates to a gas sensor for sensing the concentration of a gas component in a measurement gas to be examined.
A gas sensor of an earlier technology includes a sensing element producing a gas concentration signal representing the concentration of a gas component in a measurement gas (such as the NOx concentration of an exhaust gas of an internal combustion engine). The gas sensor is controlled by a sensor control device, which is configured to obtain the gas concentration signal from the sensing element by performing a sensor drive control of controlling a sensor main portion of the sensing element and a heater drive control of controlling a heater for heating the sensor main portion of the sensing element.
There may be subtle nonuniformity or dispersion from unit to unit in a gas concentration characteristic which is a characteristic representing a relationship between the concentration signal of the sensing element (the sensor main portion of the sensing element) and the concentration of a specified gas component, and a heater temperature characteristic which is a characteristic representing a relationship between the resistance (impedance) of the heater and the heater temperature.
Therefore, a gas sensor disclosed in a patent document JP 11-72478A (corresponding to U.S. Pat. No. 6,082,176) is provided with a storage medium for storing information (individual information) on the gas concentration characteristic and heater temperature characteristic of the corresponding gas sensor. The sensor control device obtains the stored individual information from the storage medium of the gas sensor and performs correction to reduce adverse influence of the dispersion.
Furthermore, a gas sensor disclosed in a patent document JP 2009-192486A includes a circuit board or wiring board equipped with a storage medium, a resin case including a mount surface supporting the circuit board, and a seal portion of a thermoplastic resin filled in the resin case to enclose the circuit board water-tightly.